1. Field of the Invention
The present invention relates to a magnetic recording medium used for a hard disk drive (HDD) and the like and a method of manufacturing a magnetic recording medium, and to a magnetic record/reproduction apparatus including the magnetic recording medium or a magnetic recording medium manufactured according to the manufacturing method.
This application Claims priority on Japanese Patent Application No. 2011-116149 filed on May 24, 2011, the disclosure of which is incorporated by reference herein.
2. Background Art
The perpendicular magnetic recording medium, the magnetic easy axis of which is oriented in the perpendicular direction of a medium is a suitable system to increase magnetic areal density than the system of the traditional longitudinal recording medium. The demagnetizing field decreases the thermal stability of recorded magnetization in medium; however, the demagnetizing field in the perpendicular magnetic recording medium is decreased with increasing the magnetic areal density, i.e., the perpendicular magnetic recording is recognized by researchers and engineers as the prime candidate system to realize a high area recording density over 1 tera bit per a square inch.
A perpendicular magnetic recording medium is obtained by sequentially stacking a soft magnetic underlayer, an underlayer, an intermediate layer and a perpendicular magnetic recording layer, each of which are formed of a thin film, on a disk-shaped non-magnetic substrate. In the case where the soft magnetic underlayer made of a soft magnetic material is provided between the disk-shaped non-magnetic substrate and the perpendicular magnetic recording layer, this function as a so-called double layer perpendicular magnetic recording medium, which can achieve high recording performance. The soft magnetic soft magnetic underlayer serves to reflux a recording magnetic field which is generated from a magnetic head, thereby improving the record/reproduction efficiency.
The underlayer functions to determine the grain diameters and the crystal orientations of both the intermediate layer and the perpendicular magnetic recording layer provided on the intermediate layer. In the intermediate layer, a dome-shaped convex part is formed at the top of each crystal particle, and the magnetic crystal grains such as those of a recording layer are grown on the convex parts. Thereby, the separation of the grown crystal grains promotes the isolating of the magnetic crystal grains in the recording layer, and the magnetic grains are grown in the form of columns (refer to Japanese Unexamined Patent Application, First Publication No. 2007-272990).
According to another method of manufacturing a magnetic recording medium, FePt nanoparticles are used (refer to Japanese Unexamined Patent Application, First Publication No. 2009-035769). According to this method, an FePt magnetic nanoparticle array in which the FePt nanoparticles are arranged on a substrate by coating or the like is used in the magnetic recording medium. This recording medium is superior to the current magnetic recording medium using continuous thin films due to weakening of magnetic coupling between magnetic grains.
Specifically, Japanese Unexamined Patent Application, First Publication No. 2009-035769 discloses a method of forming a mono-layer film of FePt nanoparticles by bonding a dispersant to the FePt nanoparticles and chemically bonding the dispersant to a surface of the substrate or chemically bonding the dispersant to another dispersant chemically bound to the surface of the substrate.